1. Technical Field
The present invention relates to a liquid consumption apparatus, etc.
2. Related Art
Inkjet printers are known as an example of liquid consumption apparatuses (liquid injection apparatuses). Inkjet printers can perform printing on printing media such as printing paper by ejecting ink, which is an example of a liquid, from a printing head onto the printing media. Also, inkjet printers are provided with an ink tank, which is an example of a liquid container for storing ink, and perform printing by supplying the stored ink to the printing head. Among inkjet printers of this type, some inkjet printers are known for being provided with a liquid detection unit as disclosed in JP-A-3-275360, which detects the amount of ink remaining in the ink tank, which is a kind of ink information.
In some cases, the liquid detection unit passes an electric current through the ink inside the ink tank in order to detect the amount of remaining ink. In such cases, there is the possibility of the ink being subjected to electrolysis due to the direct current passing through the ink, which leads to the occurrence of bubbles or the deposition of the ink components on the electrodes. Such a situation is problematic because the bubbles or the deposited ink components are mixed into the ink and conveyed to the printing head, clog up the nozzle of the printing head, and have a negative influence on ink ejection. The liquid detection unit according to JP-A-3-275360 is provided with a voltage limiting unit, and applies a pulse voltage also across a plurality of electrodes. Thus, JP-A-3-275360 suggests a means for detecting the amount of remaining ink while suppressing electrical energy to be applied and preventing electrolysis. However, JP-A-3-275360 does not disclose the technical concept of avoiding the negative influence of electrolysis by passing an alternating current through the ink, or any specific means for realizing the concept.
Note that an alternating current is a current with which the polarity of the voltage applied across two electrodes periodically changes with time, and the flow of the current passing between the two electrodes changes in direction along with the voltage changing. A representative example of this is a sine wave alternating current. In this specification, a sine wave alternating current and a non-sine wave alternating current are collectively referred to as an alternating current.
Regarding the case of detecting the amount of remaining ink by passing an electric current through the ink inside the ink tank, related art such as JP-A-3-275360 does not disclose a technique to appropriately position the circuit elements of a circuit substrate on which detection circuits are provided, or a technique to appropriately connect the circuit substrate to the ink tank. Note that a connection between the circuit substrate and the ink tank may be a physical connection in an appropriate relative positional relationship or an electrical connection between the circuit substrate and an electrically-conductive member (electrode rod) provided for the ink tank.
Some aspects of the invention can provide, for example, a liquid consumption apparatus that is applicable to the case of detecting a liquid surface level by using an alternating current, and in which a circuit substrate is appropriately positioned.